missfire 87 e350 460 cu in

[novadude]

goodmorning ,I have abit of a head scratcher,#3 cyl misfire.compression good 145 psi ,tail pipe readings 1700 hc 1.0% co . new tune up parts installed no different thuroghly inspected for possible vacuum leaks none found .Have a steady vacuum reading 19 in hg.inspected valve springs all ok,removed intake to inspect after installing no diff.what am I missing,any suggestions would help.Thanks in advance Rob K

[shawnlee28]

The only other culprits are ,wire ,plug ,cap,injector.
I have a 89 460 and with 4 wires one one side off it still runs decent.
Trying to pass emissions ?

[novadude]

Yes this is carburated engine with high H.C.

[R Pope]

Your first post seems to say that you installed a new intake, is that when the problem started?

[thesals]

i think he's saying he pulled the intake to inspect it for cracks...... if you've got good fuel and you got good compression the only thing that would cause your missfire would be fire..... check your ignition out... make sure all your plugs are gapped right, check continuity on your wires(should never exceed 3000ohms per foot at OEM standards but should be much lower than that if possible), inspect the cap for any cracking or burn marks( the smallest of crack can cause spark scatter). check ignition and valve timing